It would seem to me like London wouldn't want a new distribution of power from the more or less stable regime post-1815, even despite the 1848 revolutions and the Crimean war.
Yet as far as I read the UK didn't try to avoid the rise of such a behemoth as Prussia would become, even defeating Austria and France. Why?
Bonus question: How did UK policy towards Germany change with Disraeli's arrival?
In the 1860s, the worries of British statesmen with respect to Europe centered on France and Russia. A strong German confederation would serve as a counterweight to both states, thereby reducing the chances of such things as a French invasion of the United Kingdom or a Russian invasion of India.
In 1866, British sympathies lay with the states of the German Confederation that were arrayed against Prussia. (This was particularly true for the Kingdom of Hanover.) Still, there is little indication that British statesmen saw much danger coming from the direction of Prussia until after the defeat of France in the war of 1870-71.